Embodiments relate to methods of fabricating a semiconductor device. Some embodiments relate to a method of fabricating a Polysilicon-Insulator-Polysilicon capacitor.
A Polysilicon-Insulator-Polysilicon (PIP) capacitor may be used to prevent an analog device from emitting noise and/or modulation of frequency. Since a PIP capacitor may have a lower electrode and an upper electrode formed of polysilicon, which may be a similar material as a gate electrode of a logic transistor, electrodes of a PIP capacitor may be formed together with a gate electrode without separate forming processes. When a device requires relatively large capacitance, a PIP capacitor may be used.
In a PIP capacitor, there may be a structure which uses an oxide-nitride-oxide (ONO) as an insulating material and/or a structure which uses an oxide film as an insulating material. FIG. 1 illustrates a cross section of a PIP capacitor having an ONO structure. A PIP capacitor having an ONO structure may be provided with lower polysilicon electrode 122 formed on and/or over field oxide film 120 on and/or over substrate 110. ONO films 132, 134 and/or 136, and/or upper polysilicon electrode 140 may be provided. Polysilicon resistor 124 on and/or over field oxide film 120 may be formed at substantially the same time with lower polysilicon electrode 122. Gate electrode 145 may be formed at an active region at substantially the same time with upper polysilicon electrode 140.
A PIP capacitor may have capacitance fixed by a thickness of nitride 134. If nitride 134 is relatively thick, a portion of the nitride may remain on and/or over lower polysilicon electrode 122 of a PIP capacitor in etching ONO layer 130. A failure of formation of silicide 154 on and/or over lower polysilicon electrode 122 may occur during a subsequent silicide step.
FIG. 2 illustrates a cross section of a PIP capacitor having an oxide film structure. A PIP capacitor may be provided with lower polysilicon electrode 232 formed on and/or over field oxide film 220 on and/or over silicon substrate 210. Polysilicon oxide film 240, gate oxide film 250, and/or upper polysilicon electrode 260 may be provided. Polysilicon resistor 234 may be provided on and/or over field oxide film 220 and may be formed at substantially the same time with lower polysilicon electrode 232. Gate electrode 262 may be formed at an active region at substantially the same time with upper polysilicon electrode 260.
A thickness of an oxide film that may be an insulating material of a PIP capacitor having an oxide film structure may be fixed by a polysilicon oxidizing step, a gate oxide film forming step, and/or a washing step. A polysilicon oxidizing step may refer to a step of making first oxide film 240 grow on and/or over lower polysilicon electrode 232. A gate oxide film forming step may relate to a step of forming gate oxide film 250 on and/or over silicon substrate 210 at an active region. A washing step may relate to a step of removing first oxide film 240 formed substantially evenly at an active region in a polysilicon oxidizing step before a gate oxide film forming step.
A thickness of an oxide film, for example, a first oxide film and/or a gate oxide film, formed on and/or over lower polysilicon electrode 232 may be fixed by a polysilicon oxidizing step and/or a gate oxide film forming step. A washing step, which may be performed to remove first oxide film 240 from an active region before a gate oxide film forming step, may impair uniformity of a transistor formed on and/or over an active region. Moreover, an amount of loss of silicon required for growth of an oxide film may increase during the two oxidizing steps, resulting in a relative reduction of thickness of lower polysilicon electrode 232.
Accordingly, there is a need to provide a method of fabricating a PIP capacitor which may secure substantial uniformity of a transistor, formation of silicide and/or relative thickness of polysilicon of a lower electrode. There is a need to provide a method of fabricating a PIP capacitor which may maximize productivity, for example by minimizing washing and/or furnace steps.